When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
They are just Parker Vibra Lok fittings, and they along with the seals are available at pretty much any decent hydraulics shop, I have posted this many many times but noone ever seems to listen.
They go beteen the injector line and injector body. small rubber peice thats meant for places of extreme vibration, maintains a seal while allowing for a tiny bit of movement.